Outdoor solar lamps are known, such as for streets or gardens. These lamps generally consist of one or more solar modules, electrical storage means for storing electrical energy connected to the solar module and one or more bulbs that are illuminated by solar power.
Incandescent light bulbs are disadvantageous for use in such lamps. One reason is that incandescent light bulbs draw significant power, and since the lamp must work all night, the light bulb may not provide enough light towards the end of the night. The lifetime of the bulb is also shortened.
Solid state devices, such as light emitting diodes (LEDs), have been used to replace conventional light sources such as incandescent, halogen and fluorescent lamps. LEDs have substantially higher light conversion efficiencies than incandescent and halogen lamps and longer lifetimes than all three of these types of conventional light sources. Some LEDs have higher conversion efficiencies than fluorescent light sources. LEDs require lower voltages than fluorescent lamps and contain no mercury or other potentially dangerous materials, therefore, providing various safety and environmental benefits.
However, the typical LED has a diffuse emission pattern that spans a hemispherical arc. This emission pattern may limit the use of LED light sources, or other solid state lighting devices, as replacements for conventional light sources for incandescent, halogen and fluorescent lamps, which emit light in all directions. An LED light source that is used in an incandescent light bulb, for example, may result in undesired dark spots in the downward direction.